KR101907288B1 - Device for backscatter communication - Google Patents

Abstract

The backscattering communication includes receiving electromagnetic energy from the base station and encoding the first data and the second data. The first data is encoded at a first frequency by modulating the radar cross section of the device and modulating the electromagnetic energy reflected back to the base station. The second data is encoded at a second frequency by restricting adjustment of the plurality of radar cross sections for a time length to either the first subset or the second subset of the plurality of radar cross sections. The second frequency is lower than the first frequency.

Description

[0001] DEVICE FOR BACK SCATTER COMMUNICATION [0002]

<Reference to related application>

This application is related to U.S. Serial No. 14 / 502,175, Attorney Docket No. 7171P279, filed on September 30, 2014, entitled "Receiver for Backscatter Communication," which is currently pending.

<Technical Field>

This disclosure is generally directed to backscatter communication, and in particular, but not exclusively, to wireless-frequency identification (" RFID ") tags.

Radio-frequency identification (" RFID ") communication is an example of backscattering communication. RFID communications typically include a " base station transceiver " that broadcasts / transmits electromagnetic energy and then interprets the data from the reflected electromagnetic energy. A " tag " reflects a portion of the electromagnetic energy returning to the base station to communicate data to the reader. To encode the data (e.g., identification number) of the reflected portion, a passive (battery-free) tag harvests power from the broadcasted electromagnetic energy and uses the harvested power to re- Modulation is possible. Conversely, a tag for battery power supplies power to a circuit that modulates the electromagnetic energy reflected back to the base station using the battery. Passive tags generally have a much shorter range than tags for battery power.

Back scattering communications (including RFID communication systems) are becoming increasingly important because tags can be made relatively small and RFID communications do not require a line-of-site between base stations and tags. As RFID communication systems become more popular, there is a growing need to transmit larger amounts of information in shorter time periods using backscattered communications.

Non-limiting and non-exhaustive embodiments of the present invention will be described with reference to the following drawings, wherein like reference numerals refer to like parts throughout the various views unless otherwise stated.
FIG. 1 illustrates a backscattering communication system including a base station and tags, in accordance with an embodiment of the present disclosure.
2A is a functional block diagram illustrating a base station for facilitating backscatter communication, in accordance with one embodiment of the present disclosure;
2B is a functional block diagram illustrating an exemplary backscatter reception circuit in accordance with one embodiment of the present disclosure.
3A shows a block diagram of a device including an exemplary tag in accordance with one embodiment of the present disclosure.
Figure 3B shows a block diagram of a device including an exemplary tag in accordance with one embodiment of the present disclosure.
4A illustrates a chart depicting the voltage of a signal over time, in accordance with one embodiment of the present disclosure.
FIG. 4B illustrates an enlarged portion of the chart of FIG. 4A, in accordance with one embodiment of the present disclosure.
Figure 5 shows a chart representing vector radar cross sections along time of an antenna, in accordance with one embodiment of the present disclosure.
6 shows a flow diagram illustrating a tag-side method of backscattering communication, in accordance with an embodiment of the present disclosure;
7 shows a flow diagram illustrating a backscattering communication method using a base station, in accordance with an embodiment of the present disclosure;

Embodiments of systems and methods for backscattering communications are described herein. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the embodiments. However, those of ordinary skill in the pertinent art will recognize that the techniques described herein may be practiced without one or more of the specific details, or with other methods, components, materials, or the like. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring certain aspects.

Reference throughout this specification to " one embodiment " or " an embodiment " means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention . Thus, the appearances of the phrases " in one embodiment " or " in one embodiment " in various places throughout this specification are not necessarily all referring to the same embodiment. Moreover, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

1 illustrates a backscattering communication system 100 that includes tags included in a base station transceiver 103 and a mobile device 101 in accordance with one embodiment of the present disclosure. The backscattering communication system 100 may use backscattering communications to provide a short range (e.g., up to 20 m), high bandwidth (e.g., 20 to 100 Mbps), and low (e.g., To communicate data from one or more mobile devices (101) to the base station (103). An example of backscattering communication is generally known as radio frequency identification (" RFID "). RFID is often used to wirelessly communicate identification codes of objects (e.g., key cards, consumer products). However, backscatter communication, including RFID, can also be used to stream larger sets of data than simple identification codes / numbers

The backscattering communication link is achieved by incorporating backscatter tags (e.g., semi-passive tags) into the mobile devices 101. The design provides a low power solution on the mobile station device side by leverage the asymmetric power budget between the wireline base station 103 and the mobile devices 101 to rely on readily available power at the base station side.

The base station 103 includes one or more antennas that broadcast electromagnetic ("EM") energy 104 toward the mobile device 101 and receive the modulated backscattering reflection 105 of the EM energy 104. The modulated backscattering reflection 105 is referred to as a backscattering signal or a backscattering channel. Back scattering tags incorporated into the mobile device 101 do not transmit any RF or microwave power. Rather, they operate by modulating the reflection of the EM energy 104. The backscattering reflection is encoded into data by modulating the radar signature or radar cross section of the mobile device 101 with the data and the base station 103 demodulates the received radar signature reflected from the mobile device 101 to extract the embedded data . One technique for modulating the radar cross section of the mobile device 101 is to modulate the impedance load coupled to the backscattered antenna on the mobile device 101. This impedance modulation is a low-power operation compared to active transmitters such as WiFi or Bluetooth radio.

Some radio frequency identification (" RFID ") tags are complete passive devices that do not include an independent power source and harvest their energy for operation from the EM energy 104. However, the energy harvest from the EM energy 104 does not improve the data rate of the backscattered channel since the backscattered antenna is generally optimized for power harvesting and does not necessarily improve the signal-to-noise ratio (" SNR & In fact, slow. In addition, fully passive RFID tags are often suspended for periodic power harvesting, which interferes with or delays data transmission. Energy harvesting reduces the read range for base station 103 because more incident EM radiation 104 needs to be powered up in the backscatter tag than is required for backscatter communication only. Conventional fully passive backscatter tags use a slower data rate because the energy consumption of the backscatter tag is highly dependent on the clock speed.

Embodiments of the back scattering tags embedded in the mobile device 101 may be partial passive devices that do not harvest energy from the EM radiation 104. Rather, backscatter tags are powered by the main battery of the mobile device 101. Since modulating the impedance load requires an appropriate power budget (e.g., 15 pF), backscatter transmission does not affect battery life in an important way. In addition, by not harvesting power from the EM energy 104, the backscattering antenna and the modulation load impedance reflect the EM energy 104 to improve SNR, reduce bit rate error, and reduce the data throughput of the backscattered channel Gt; &lt; / RTI &gt; By not harvesting power from the EM energy 104 to power the backscatter tag, some embodiments described herein can operate at higher clock rates and greater data throughput. Other embodiments of the present disclosure may harvest energy from the EM energy 104.

The EM energy 104 may be broadcast using a variety of different carrier frequencies. For example, the EM energy 104 may operate on undisturbed frequencies such as 915 MHz, 2.45 GHz, 5.8 GHz, and 61.25 GHz. The backscatter tags can modulate the backscatter signal using various techniques and symbol constellations for encoding data on the backscattered channel. For example, binary phase shift keying (" BPSK ") or binary amplitude shift keying (" BASK ") may be used. In order to achieve a higher data rate, quadrature amplitude modulation (" QAM ") can be used to modify the vector radar cross section (" RCS ") of the antenna by modulating the load impedance applied to the backscattered antenna. Using a higher carrier frequency and a larger QAM arrangement (e.g., 16-QAM, 64-QAM, etc.) can achieve higher data rates (e.g., 100 Mbps). In some embodiments, the symbol constellation for encoding data on the backscattered channel may improve throughput, improve SNR, or degrade performance as the mobile device 101 moves through its environment And may be adaptively updated based on the environment (e.g., noise, multi-path reflections, etc.) so that the scatter link is less sensitive.

The mobile device 101 may be a mobile phone 101A, a head wearable display 101B, a smart wrist watch 101C, a tablet, a laptop, a body-mountable device, a body implant, &Lt; / RTI &gt; and various other devices including mobile devices. The embodiments disclosed herein provide a backscattering channel with sufficient bandwidth to wirelessly stream data (e.g., video data, audio data, text data) from the mobile device 101 to the base station 103. The base station 103 may then transmit streamed data over a wired (e.g., Ethernet) or wireless (e.g., WiFi) connection to other devices such as televisions, servers, or other mobile devices can do. In the illustrated embodiment, base station 103 is a stand-alone box. In other embodiments, base station 103 may be integrated into a television, a home computer, a computer monitor, a WiFi access point, a cable modem, a hard drive, a router, a set top box, or other electronic device. In one embodiment, where the base station 103 is at a WiFi access point or included in a WiFi access point, the EM energy 104 may be a WiFi transmission and the tags may reflect the EM energy 104 back to the base station 103.

FIG. 2 is a functional block diagram illustrating an exemplary base station 203 for facilitating backscatter communication, in accordance with one embodiment of the present disclosure. The base station 203 is one possible implementation of the base station 103 shown in FIG. The depicted embodiment of base station 203 includes a backscattering transceiver 205, backscattering antennas 210 and 215, control circuit 220, wired interface (s) 230, power regulator 235, (S) &lt; / RTI &gt; The illustrated embodiment of the backscattering transceiver 205 includes a backscattering transmit circuitry 245 and a backscattering receive circuitry 250. [ The illustrated embodiment of the control circuit 220 includes logic 287. [ Figure 2 shows the functional components of the base station 203 and need not necessarily be a structural layout. It should be appreciated that the components of base station 203 may be implemented entirely in hardware, in software / firmware as a whole, or in a hybrid of software / firmware and hardware.

The backscattering transceiver 205 is a communication channel for communicating high bandwidth data from the mobile device 101 to the base station 203. In one embodiment, the upstream direction from the backscatter transmission circuit 245 is a non-communication path, but only outputs the EM energy 212 as a kind of radar signal. In other embodiments, the backscatter transmission circuitry 245 may modulate the data with the EM energy 212 to provide an upstream broadcast data path to the mobile device 101. Backscatter transmission circuit 245 may output EM energy 212 having a variety of different frequencies such as 915 MHz, 2.45 GHz, 5.8 GHz, 61.25 GHz, or the like. The backscatter reception circuitry 250 operates by implementing a downstream path from the mobile device 101 and demodulating the backscattered signal reflected by the mobile device 101. In essence, the backscattering reception circuit 250 demodulates the received radar signature reflected from the mobile device 101. The radar signature or backscatter signal may be modulated using a variety of different techniques and symbol arrays, including BPSK, BASK, QAM or the like. As such, the backscattering receiver circuit 250 includes filters, mixers, amplifiers, decoders, framers, and the like, needed to demodulate / decode the appropriate modulation scheme. Although FIG. 2 shows separate transmit and receive antennas, in other embodiments, a single backscattered antenna may be used to transmit EM energy 212 and receive backscatter signal 217. In another embodiment, multiple transmit and receive antennas may be used with beam forming and tracking techniques.

The wireless interface (s) 240 represents one or more wireless communication channels that do not use backscatter communication. For example, the wireless interface (s) 240 may be implemented using a WiFi transceiver, a Bluetooth transceiver, an infrared transceiver, or other standardized / proprietary wireless communication system. The wireless interface (s) 240 may facilitate non-backscatter communication with the mobile device 101 or other device. The wireless interface (s) 240 may also provide a wireless network connection to the Internet or other consumer products (e.g., network attached storage, etc.) for the base station 203.

The wired interface (s) 230 may include any number of wired communication ports. For example, the wired interfaces 230 may include an Ethernet controller, a universal serial bus (USB) port, or the like. The Ethernet controller may provide a network connection.

The power adjuster 235 provides a wired power connection for powering the internal components of the base station 203. Since base station 203 is a wired device, it is not constrained by a limited power budget, such as mobile device 101. [ Backscattering communications are generated by the generation of power-hungry EM energy 212 while the mobile device 101 operates by reflecting EM energy 212 generated at base station 203 (rather than generating EM radiation independently) To the base station 203 to leverage this asymmetric power budget.

The control circuit 220 is an operation brain of the base station 200. It includes logic 287 for coordinating the operation of other functional components and includes a processor and / or a field-programmable gate-array (" FPGA ") for performing calculations. The logic 287 may comprise hardware logic or software / firmware instructions stored in one or more memory devices. For example, logic 287 may comprise instructions for establishing a wireless session with one or more mobile devices 101, configuring and managing a wireless display session, and terminating a wireless display session.

Many commercial backscatter tags operate by encoding data using two separate states. However, by using a larger number of states (increasing the array of available communication symbols), quadrature amplitude modulation (" QAM ") can be achieved to communicate higher data rates in backscattered communications. For example, using 16 states (e.g., 16-QAM), the data rate can be increased four times in the tradeoff of lower SNR. In addition, it has been shown that pairing the increased data frequency with the increase of the communication symbols enables a very high data rate (e.g. ~ 100 Mbps). Higher data rates can be used to stream data (e.g., cloud backups, video data) for large data applications.

To increase the array of available communication symbols beyond two data states (e. G., Digital 0 and 1), the tag associated with the backscattered communication must be able to generate an increased number of communication symbols. In addition, generating an increased number of communication symbols at higher frequencies allows high-speed channels with higher data rates than are available in the prior art. However, in order to ensure that the tag can communicate using the conventional low-speed scheme (with two data states), a tag capable of communicating data using both the low-speed scheme and the disclosed high-speed data transmission would be advantageous . Thus, the tags disclosed in this disclosure are not only backwards compatible with the conventional (e.g., " Gen 2 ") low rate RFID protocol, but also achieve high data transmission so that the tags communicate with existing base stations utilizing existing RFID protocols . Conventional low speed data can be transmitted at 125 kHz, while high speed data can be transmitted at 25 MHz.

3A shows a block diagram of an exemplary device 310A including an exemplary tag 307A, in accordance with an embodiment of the present disclosure. The device 310A may be one of the mobile devices described in FIG. Exemplary device 310A includes a battery 325, a processor 350, a sensor 375, a first analog to digital converter (" ADC ") 361, a second ADC 363, and an antenna 345 . The tag 307A includes a modulation circuit 330 and an encoding module 320. [

Antenna 345 is configured to receive electromagnetic radiation / energy (e.g., EM energy 212) from an antenna of a backscattered base station, such as antenna 210 of base station 203. The antenna 345 may also be configured to receive cellular data (e.g., 3G, 4G, LTE), WiFi (e.g., IEEE 802.11) and / or Bluetooth data. In other words, the existing antenna on the mobile device can be used for backscattering communication.

The modulation circuit 330 is coupled to a modulating antenna 345 with a plurality of impedance values (Z ₀ -Z _{31 in} FIG. 3A) applied between the antennas. Changing the impedance values of the antenna 345 is one way of changing the vector radar cross section of the device 310A. Changing the vector radar cross section will cause the back scatter signal 217, which the antenna 345 reflects back to the base station 203, to change so that the tag 307A can communicate data back to the base station 203.

The modulation circuit 330 includes an A 'modulation circuit 331, a B' modulation circuit 332, and a 2-1 multiplexer (" MUX &quot;) 339. The A 'modulation circuit may only modulate the impedance of the antenna 345 where the impedance values Z ₀ -Z ₁₅ are between the first subset. The impedances Z ₀ -Z ₁₅ serve to communicate the 16 symbols available for communicating with the base station 203 (e.g., to implement 16-QAM signaling). The B 'modulation circuitry can only modulate the impedance of the antenna 345 where the impedance values Z ₁₆ -Z ₃₁ are between the second subset. The impedances Z ₁₆ -Z ₃₁ function as 16 corresponding symbols communicating the same symbols as the impedances Z ₀ -Z ₁₅ . For example, in one embodiment, adjusting antenna 345 to impedance Z ₀ will communicate the same symbol to base station 203 as adjusting antenna 345 to impedance Z ₁₆ . In this example, Z ₀ and Z ₁₆ are corresponding impedances communicating corresponding identical symbols. It is understood that having only 32 impedance values (Z ₀ -Z ₃₁ ) including a subset of the 16 impedance values is exemplary only, and that more or fewer impedance values can be used in different embodiments .

Encoding module 320 includes A 'selector logic 325 and B' selector logic 327. The encoding module 320 encodes the first data (391) in the first high frequency (CLK1) by indicating to select between modulation circuit 330, a plurality of impedance Z ₀ -Z _31. Encoding module 320 may also be configured to instruct modulation circuit 330 to select between a first subset Z ₀ -Z ₁₅ or a second subset Z ₁₆ -Z ₃₁ of the plurality of impedance values Z ₀ -Z ₃₁ , And to encode the second data 392 in the second clock signal CLK2. CLK2 operates at a frequency lower than CLK1.

In Figure 3a, the A 'selector logic 325 is coupled to receive first data 391 and CLK1 operating at a first frequency. The A 'selector logic 325 is coupled to encode the first data 391 at the first frequency by directing the A' modulation circuit 331 to select between Z ₀ -Z ₁₅ . The B 'selector logic 327 is also coupled to receive the first data 391 and CLK1. The B 'selector logic 327 is coupled to encode the first data 391 at the first frequency by instructing the B' modulation circuit 332 to select between Z ₁₆ -Z ₃₁ . The MUX 339 is coupled to receive the data 392. The digital value of the second data 392 changes corresponding to the first data 391 and the frequency CLK2 which is lower than the frequency of CLK1. The digital value of the data 392 causes the 2-1 MUX 339 to couple the impedance values from the A 'modulation circuit 331 or the B' modulation to the antenna 345. The impedance value applied to the antenna 345 is limited to a first subset of the impedance values of the A 'modulation circuit 331 when the second data 392 has a first state (e. G., Digital 0) And the impedance value applied to the antenna 345 is limited to a second subset of the impedance values of the B 'modulation circuit 332 when the second data 392 has a second state (e.g., Digital 1) .

The A 'selector logic 325 and the B' selector logic 327 may be implemented using a microcontroller, a logic array, discrete logic, or an application-specific integrated circuit (ASIC). A 'modulation circuit 331 may be implemented with transistors T ₀ -T ₁₅ that may be activated to connect different impedance values Z ₀ -Z ₁₅ to MUX 339 (and ultimately antenna 345). Similarly, the B 'modulation circuit 332 may be implemented with transistors T ₁₆ -T ₃₁ that can be activated to connect different impedance values Z ₁₆ -Z ₃₁ . Of course, other non-transistor switches that can switch at high frequencies can be used instead of transistors. In addition, those of ordinary skill in the art will appreciate that alternative techniques and configurations for connecting different impedance values to the antenna 345 may be implemented.

5A, which further illustrates a method for communicating both high and low rate data streams via back scattering techniques. Figure 5 shows a chart representing vector radar cross sections (" RCSs ") over time of an antenna in a tag, according to one embodiment of the present disclosure. It is understood that the vector RCS values in FIG. 5 are examples for conveying the entire concept of providing different vector RCS values to the antenna, but in operation the vector RCSs will strictly include more complex vector RCSs than the actual vector RCS values. In addition, the impedance values applied to the antenna to give a given vector RCS value to the antenna may be a complex impedance value. 5 shows a first period, a second period, a third period and a fourth period. Each period corresponds to a period associated with the frequency of CLK2. The collection of vector RCS values for the first period, the second period, the third period and the fourth period is illustrated by groups 401, 402, 403 and 404, respectively.

In a first period, the antenna 345 is configured to encode the first data 391 as different symbols corresponding to a first subset of the impedance values (e.g., Z ₀ -Z ₁₅ ) (By applying different impedance values to the RCSs 345). In the second period, the antenna 345 is also modulated with different vector RCS values to encode the first data 391 as different symbols corresponding to the second subset of impedance values. The first group of vector RCS values 401 is closer to the center radar value 421 while the second group of vector RCS values 402 is closer to the center radar value 422. [ If the vector RCS value of the antenna 345 is closer to the central radar value 421 during the period of CLK2 then the vector RCS values closer to the central radar value 422 during the period of CLK2 are the second (E.g., digital 0) of the second data 392 while communicating the data state (e. G., Digital 1). Thus, the groups 401, 402, 403 and 404 communicate that the second data 392 is 0-1-0-0 in the first period, the second period, the third period and the fourth period of FIG. 5 . In this way, by modulating the antenna 345, the tag 307A can communicate the first data 391 as high-speed data corresponding to CLK1, and can also communicate with the first subset of impedance values and the second of the impedance values It is possible to communicate the second data 392 as low-speed data corresponding to CLK2 by switching between the sub-sets and encoding the second data. Because the tag must switch between a subset of the impedance values to communicate the low speed data, each symbol in the array of communicated symbols has a first subset of the impedance values and impedance values in the first subset communicating the symbol, Set or a second subset of the second subset communicating the symbol so that a particular high-rate symbol can be communicated regardless of whether a second subset is to be used. Of course, the impedance values that are modified (to change the vector RCS of the antenna) are modulated by adjusting the in-phase and out-of-phase (i.e., I and Q quadrature) characteristics of the backscattered signal reflected back to the base station Implementation.

The base station receiving the backscattering from the tag 307A outputs the cutoff frequency between the first frequency CLK1 and the second frequency CLK2 to the filter (either analog or digital) to separate the second data 392 Can be applied. Applying the filter will filter the higher frequency data, but the combination of higher frequency symbols will still arrive closer to the radar signal corresponding to the central radar value 421 or the central radar value 422, 392). &Lt; / RTI &gt; It is understood that the word " center " in the term &quot; central radar value &quot; may be associated with a particular mapping (e.g., a specific area of a Smith chart) from a backscattered signal to a signal received by the base station. This mapping is not necessarily linearly related to the tag impedances but is not necessarily uniformly distributed, but heavily depends on the RF link between the tag and the base station, and is highly dependent on the arrangement of the adopted vector RCS values.

3A, the sensor 375 is coupled to provide a signal 371 to both ADC1 361 and ADC2 362. Signal 371 may be voltage, current or otherwise. Sensor 375 may be, for example, a biometric sensor that measures glucose or heart rate. ADC1 361 samples signal 371 at a first frequency associated with CLK1. ADC2 362 samples signal 371 at a second frequency associated with CLK2.

4A and 4B show that the first frequency CLK1 is higher than the second frequency CLK2. FIG. 4A is a chart showing the voltage of the signal 471 over time, and FIG. 4B shows an enlarged portion of the chart of FIG. 4A, according to one embodiment of the present disclosure.

Signal 471 is an example of signal 371. The first data 391 has a higher resolution than the second data 392 because the ADC1 361 samples the signal 471 at a faster rate than the ADC2 362 samples the signal 471. [ In one example, only one ADC is used to sample the signal at the first frequency (CLK1) and a subset of the sampled signal at the second frequency (CLK2) is transmitted as the second data 392. For example, the ADC may select every tenth or every 100th sample corresponding to the second data 392. [ Alternatively, the data from one ADC may be processed to provide summary data as second data 392. One application for this implementation would transmit an electrocardiogram (" ECG ") cardiac signal that still shows diagnostic details at higher frequencies, but lower frequencies still indicate pulses per minute. When the tag 307A simultaneously encodes the first data 391 and the second data 392 by changing the impedance of the antenna 345, the high-resolution first data 391 and the low- Both sides can be encoded. Thus, the base station configured to read the high speed data protocol will be able to receive the first data 391 of high resolution. However, if the base station is not configured to read the high speed data protocol (legacy base station), it will still be able to read the low speed data protocol and still be able to receive the low speed data 392. The low speed data 392 protocol may be backward compatible EPC Gen2 so that legacy base stations can read low speed data 392.

Processor 350 may also be coupled to transmit data to tag 307A for backscatter communication. In one embodiment, the processor 350 accesses the memory and the processor transmits data from the memory to the tag 307A to transmit data to the base station. In one embodiment, the medical record is stored in memory and processor 350 facilitates streaming medical records to the base station using tag 307A. In one embodiment, processor 350 is the main processor of device 310A. In one embodiment, the first data 391 and the second data 392 comprise the same data content. As a result, the first data 391 is simply encoded faster than the second data 392, and the base station configured to receive the fast protocol will receive the data content faster on the fast channel. However, the legacy base station will still be able to receive the same data content as the second data 392 on the slow channel. This arrangement allows the updated base station to receive data from the tag 307A sooner, while allowing the un-updated base station to still receive the same data, albeit slowly.

FIG. 3B shows a block diagram of a device 310B including an exemplary tag 307B, in accordance with an embodiment of the present disclosure. Tag 307B represents a different hardware configuration that performs the same function as described with respect to tag 307A. The tag 307B includes an encoding module 340 and a modulation circuit 351. [ The modulation circuit 351 is coupled to a modulating antenna 345 between the plurality of impedance values Z ₀ -Z _N. Encoding module 340 is a modulation circuit 351 is that the impedance values Z ₀ -Z _N To encode the first data at the first frequency. Encoding module 340 is also coupled to encode the second data at a second frequency by instructing modulation circuit 351 to select either the first subset or the second subset of the plurality of impedance values Z ₀ -Z _N , do. Encoding module 340 includes selector logic 343. The selector logic 343 may be implemented as a microprocessor or as separate logic. The selector logic 343 receives the first data 391 and the second data 392. When the second data 392 is in a first data state (e.g., digital 0), the selector logic 343 limits the selection of its impedance values Z ₀ -Z _N to the first subset of impedance values. When the second data 392 is in a second data state (e.g., Digital 1), the selector logic 343 limits the selection of its impedance values Z ₀ -Z _N to the second subset of impedance values.

The device 310B includes a sensor 377, a sensor 379, a first ADC 361, and a second ADC 363. The sensor 377 provides the signal 372 to the first ADC 361 and the sensor 379 provides the signal 373 to the second ADC 363. The sensor 379 may be a heart rate sensor, while the sensor 377 may sense audio data (i.e., a microphone). In one embodiment, a sensor requiring a lower data rate is coupled to produce second data 392 while a sensor requiring a higher data rate is coupled to produce first data 391. It is understood that the different sensor configurations shown in Figs. 3A and 3B can be used to generate the first data 391 and the second data 392.

In the examples shown in FIGS. 3A and 3B, the first subset of impedance values may include impedance values common to the second subset of impedance values. In a different embodiment, the first subset of impedance values may not share the impedance values with the second subset of impedance values.

After the tag 307A or 307B encodes the data into the backscatter signal 217, the backscatter signal 217 is received by the antenna 215 and decoded by the backscatter receiver circuit 250. 2B is a functional block diagram illustrating backscatter reception module 251 as one possible example of backscatter reception circuit 250, in accordance with an embodiment of the present disclosure.

The backscattering reception module 251 includes a mixing block 252, a front-end module 255, and a decoding module 280. The front-end module 255 includes a low-pass filter 256 and a high-speed filter 257. The decoding module 280 includes a fast decoding module 281 with a symbol conversion unit 282. The decoding module 280 also includes a low rate decoding module 283. The backscattering receive module 251 may include additional analog and / or digital filters, ADCs, framing and equalization modules and circuitry not specifically shown to obscure the present invention.

Mixing block 252 is coupled to receive back scatter signal 217 from receive antenna 215 and is coupled to receive carrier frequency 253. The carrier frequency 253 will be equal to the frequency of the EM energy 212 (transmitted signal) and the mixing block 252 will generate a backscatter signal 217 ) Is multiplied by the carrier frequency 253. The modulated portion of the backscatter signal goes to the front-end module 255. Both the high speed filter 257 and the low speed filter 256 receive a backscattering signal as configured in parallel in FIG. The backscattering signal can be selectively amplified before reaching the filter.

Low-speed filter 256 is configured to separate low-speed data from high-speed data. High speed data is encoded into the backscatter signal 217 by a tag (e.g., 307A or 307B) at a first frequency (e.g., 25 MHz) and low speed data is encoded at a second frequency (e.g., 125 kHz) The low speed filter 256 separates the low speed data by filtering the frequency of 125 kHz or more. For example, the low-pass filter 256 may be a low-pass filter having a cut-off frequency between the first frequency and the second frequency. Thus, the low pass filter 256 passes the low speed data 259 in response to the back scatter signal. Because the low-pass filter 256 filters fast transitions of high-speed data, the values of the fast symbols are effectively averaged. This filtering determines whether there are high-speed symbols among the first subset of symbols or the second subset of symbols at a given time since the value of the low-rate data indicates which subset of the symbols was used for a given time . If fast symbols are received in the first subset (for a fixed length of time), this indicates a first state (e.g., 0) of low speed data and fast symbols are received in the second subset If received, it indicates a second state of slow data (e.g., digital 1). The length of time that high-speed symbols need to stay in the subset to indicate a particular data state corresponds to a period of the second frequency (e.g., 125 kHz).

The fast symbols include a first subset of symbols and a second subset of symbols. A first subset of the symbols may correspond to a first subset of the impedance values described in Figures 3A and 3B. Similarly, the second subset of symbols may correspond to a second subset of the impedance values described in Figures 3A and 3B. Each symbol of the first subset includes a tag 307 that includes a complete array of symbols, a first subset of the vector radar cross-section of the antenna (which is generated by the first subset of impedances) 2 &lt; / RTI &gt; subset (which is generated by the impedance of the second subset of impedances) of the second subset. The corresponding symbols communicate the same data value even though different symbols are used. In one embodiment, Z ₀ corresponds to Z ₁₆ , Z ₁ corresponds to Z ₁₇ , and ... Z ₁₅ corresponds to Z ₃₁ . Thus, in that embodiment, if Z ₀ or Z ₁₆ is given to antenna 345, it communicates the same symbol or data character.

The high speed filter 257 is configured to pass the high speed data 258 in response to receiving the back scatter signal. The high-speed filter 257 may include a band-pass filter to separate high-speed data. One or both of the high-speed filter 257 and the low-speed filter 256 may be implemented by a processor configured in software-defined-radio.

The fast decoding module 281 receives the high speed data 258 and the low speed decoding module 283 receives the low speed data 259. The fast decoding module 281 is configured to generate the first data 271 by decoding fast symbols encoded at a first frequency (e.g., 25 MHz). The tag 307 can encode high-speed symbols at the first frequency (CLK1) by modulating the impedance of the antenna 345. [ If the tag 307 uses QAM, the fast decoding module 281 will include a QAM decoding unit. Low-speed decoding module 283 is configured to output second data 272 in response to low-speed data 259 encoded at a second frequency (e.g., 125 kHz). The tag 307 can be used to determine the impedance at the second frequency CLK2 by driving the MUX 339 to limit the impedance value of the antenna 345 to the first or second subset of impedance values corresponding to the circuit 331 or 332. [ Low-speed data can be encoded.

The fast decoding module 281 includes the 2-1 symbol conversion unit 282 of FIG. 2B. Because the fast symbols comprise a first subset and a second subset of symbols and a given symbol of the first subset has a corresponding symbol of the second subset communicating the same symbol or data character, the symbol conversion unit 282 ) Outputs the appropriate data character in response to receiving either of the corresponding symbols. The decoding module 280 may also include a checksum to ensure accurate data reception.

6 shows a flow diagram illustrating the process of tag-side backscattering communication, in accordance with an embodiment of the present disclosure; The order represented by some or all of the process blocks in process 600 should not be considered to be limiting. Rather, those of ordinary skill in the art having the benefit of this disclosure will appreciate that some process blocks may be executed in various orders, or even in parallel, not shown.

At processing block 605, electromagnetic energy (e.g., EM energy 212) is received from the base station. At processing block 610, the first data is encoded (at the first frequency) by adjusting the radar cross section of the device between the plurality of radar cross sections. In the examples shown in FIGS. 3A and 3B, the vector radar cross section of the antenna 345 is adjusted by modulating the impedance of the antenna between a plurality of impedance values. However, there is an additional way to adjust the radar cross section of the device. For example, micro-electro-mechanical systems (MEMS) can be manipulated to change the radar cross-section of a device. For example, a MEMS that adjusts the tilt of a radar reflective material (e.g., a metal) also changes the radar cross section of the device. In addition, multiple MEMS can be manipulated in a pattern (in addition to tilt control) to produce different radar cross sections. Another way to adjust the radar cross-section of the device involves injecting metal objects into the liquid crystal and using liquid crystals to control the alignment of the metal objects and in turn changing the radar cross section of the device. Here again, the array of independently selectable liquid crystals with implanted metal will also produce additional tuning capabilities of the radar cross section to produce a plurality of different radar cross sections. Additional ways to adjust the radar cross section include varactors, PIN diodes, variable attenuators, and variable phase shifters.

At processing block 615, the second data is encoded (at a second frequency lower than the first frequency) by restricting coordination of the plurality of radar cross sections for a period of time. This period corresponds to the period of the second frequency. The process 600 continues to encode the first data and the second data as needed to communicate the required amount of data to the base station.

7 shows a flow diagram illustrating a backscattering communication method using a base station, in accordance with an embodiment of the present disclosure; The order represented by some or all of the process blocks in process 700 should not be considered to be limiting. Rather, those of ordinary skill in the art having the benefit of this disclosure will appreciate that some process blocks may be executed in various orders, or even in parallel, not shown.

At processing block 705, a backscatter signal (e.g., backscatter signal 217) is received by a backscattered reception antenna (e.g., antenna 215). The backscatter signal is a modulated version of the electromagnetic transmission signal transmitted by a transmitting antenna (e.g., antenna 210). In some embodiments, the backscattering receive antenna and the transmit antenna may be the same antenna. The transmitted signal may be reflected back as a backscattered signal modulated by the tag (e.g., tag 307) of the mobile device (e.g., device 310).

The fast symbols encoded in the backscattering signal are decoded at process block 710. [ The fast symbols are encoded into a backscattering signal at a first frequency (e.g., 25 MHz).

At processing block 715, the fast symbols are converted to first data (e.g., data 271). The fast symbols include a first subset of symbols and a second subset of symbols. Corresponding symbols from the first subset and the second subset are transformed to have the same data character in the first data.

At process block 720, the second data (e.g., data 272) is decoded in response to low speed data encoded with a backscattering signal. The low rate data is encoded into a backscattered signal at a second frequency (e.g., 125 kHz) that is less than the first frequency at which the high speed symbols are encoded. Tag 307A transmits a first subset of high-speed symbols during a time length (e.g., between CLK2 signals) to indicate a first state of the second data (e.g., digital 0) Because the second data is encoded by transmitting a second subset of high-speed symbols to indicate a second state of the data (e.g., digital 1), the second data is generated such that the high- And acquires a second state when the high speed symbols are in the second subset during the time length. In one embodiment, the time length corresponds to a period of the second frequency.

It is understood that processing blocks 710/715 and 720 may be executed in parallel (as shown) or may be executed in series. Process 700 may be repeated to continuously decode the data from the backscatter signal. The base station using the process 700 will be able to decode high speed data as well as support low speed data. Thus, a tag that transmits only low-rate data will be compatible with the base station, and a tag that transmits only high-speed data (e.g., using QAM) may also be compatible with the base station. In addition, a tag (e.g., tag 307) that is capable of transmitting both low-rate and high-speed data may be compatible with a base station (e.g., base station 203) using process 700 .

The processes described above are described in terms of computer software and hardware. The described techniques may constitute machine-executable instructions embodied in a type or non-transitory machine (e.g., computer) readable storage medium, which, when executed by a machine, cause the machine to perform the described operations will be. In addition, these processes may be embodied in hardware, such as an application specific integrated circuit (ASIC) or the like.

Type of non-volatile machine-readable storage medium may be any type of non-volatile machine-readable storage medium accessible by a machine (e.g., a computer, a network device, a personal digital assistant, a production tool, any device having a set of one or more processors, And includes any mechanism for providing (i.e., storing) information. For example, the machine-readable storage medium can be any type of storage medium such as a recordable / non-recordable medium (e.g., read only memory (ROM), random access memory (RAM), magnetic disk storage medium, optical storage medium, ).

The foregoing description of illustrated embodiments of the invention, including what is described in the abstract, is not intended to be exhaustive or to limit the invention to the precise form disclosed. While specific embodiments of, and examples for, the invention are described herein for illustrative purposes, various modifications are possible within the scope of the invention, as would be recognized by one of ordinary skill in the art.

These modifications may be made to the invention in light of the above detailed description. The terms used in the following claims should not be construed as limiting the invention to the specific embodiments disclosed herein. Rather, the scope of the present invention should be determined entirely by the following claims, which are to be construed in accordance with the principles of the interpreted claims.

Claims (25)

As a mobile device,
An antenna configured to receive electromagnetic energy from an RFID base station;
A modulation circuit coupled to modulate the antenna between a plurality of impedance values to communicate with the RFID base station through backscattering of the electromagnetic energy to alter a radar cross section of the mobile device; And
Wherein the modulation circuit is coupled to encode the first data at a higher frequency by instructing the modulation circuit to select between the plurality of impedance values during a time length and wherein the modulation circuit further comprises a first subset or a second subset of the plurality of impedance values Wherein the first data state of the second data is represented by selecting from the first subset during the time length, and the second data state of the second data is represented by the second data The second data state of the second subset being represented by selecting from the second subset during the time length,
. The method according to claim 1,
And a biometric sensor coupled to generate at least one of the first data or the second data. The method according to claim 1,
Wherein the antenna is further configured to receive at least one of WiFi or cellular data. The method according to claim 1,
Wherein the first data is a high-resolution version of the second data. 5. The method of claim 4,
A first analog-to-digital converter (" ADC &quot;) configured to sample the first signal at the higher frequency to generate the first data; And
And a second ADC configured to sample the second signal at the lower frequency to generate the second data. The method according to claim 1,
Wherein the first subset of the plurality of impedance values comprises impedance values common to a second subset of the plurality of impedance values and also includes impedance values different from the second subset of the plurality of impedance values. The method according to claim 1,
Wherein the encoding module includes first selector logic coupled to select impedance values from the first subset in response to the first data and wherein the encoding module is responsive to the first data to determine an impedance Wherein the encoding module is configured to connect the antenna to the impedance values from the first subset when the second data has the first data state, And the encoding module is configured to connect the antenna to the impedance values from the second subset when the second data has the second data state. The method according to claim 1,
Wherein the first subset of the plurality of impedance values do not share impedance values with the second subset of the plurality of impedance values. The method according to claim 1,
Wherein the mobile device comprises one of a mobile phone, a head wearable display, a wrist watch, a body-mountable device, a body-portable device, a tablet or a laptop. The method according to claim 1,
Wherein the time length corresponds to the period of the lower frequency. As a wireless-frequency identification (" RFID &quot;) tag,
A modulation circuit coupled to modulate an antenna between a plurality of impedance values to communicate with an RFID base station to alter a radar cross section of the RFID tag, the antenna configured to receive electromagnetic energy from an RFID base station; And
Wherein the modulation circuit is coupled to encode the first data at a higher frequency by instructing the modulation circuit to select between the plurality of impedance values during a time length and wherein the modulation circuit further comprises a first subset or a second subset of the plurality of impedance values Wherein the first data state of the second data is represented by selecting from the first subset during the time length, and the second data state of the second data is represented by the second data The second data state of the second subset being represented by selecting from the second subset during the time length,
. 12. The method of claim 11,
Wherein the encoding module includes first selector logic coupled to select impedance values from the first subset in response to the first data and wherein the encoding module is responsive to the first data to determine an impedance Wherein the encoding module is configured to connect the antenna to the impedance values from the first subset when the second data has the first data state, And the encoding module is configured to connect the antenna to the impedance values from the second subset when the second data has the second data state. 12. The method of claim 11,
Wherein the first subset of the plurality of impedance values comprises impedance values common to a second subset of the plurality of impedance values and also includes impedance values different from the second subset of the plurality of impedance values. 12. The method of claim 11,
Wherein the first subset of the plurality of impedance values do not share impedance values with the second subset of the plurality of impedance values. 12. The method of claim 11,
Wherein the first data is a high-resolution version of the second data. 12. The method of claim 11,
The antenna is also configured to receive at least one of WiFi, Bluetooth, or cellular data. A backscattering communication method comprising:
Receiving electromagnetic energy from a base station;
Encoding the first data by modulating the radar cross section of the device between a plurality of radar cross sections of the device at a first frequency thereby modulating the electromagnetic energy reflected back to the base station; And
At a second frequency, the adjustment of the plurality of radar cross sections is limited to one of a first subset or a second subset of the plurality of radar cross sections for a time length corresponding to one period of the second frequency, Wherein the first data state of the second data is represented by selecting from the first subset during the time length and the second data state of the second data is represented by selecting from among the second subset during the time length, Wherein the second frequency is less than the first frequency. 18. The method of claim 17,
Wherein the first subset of the plurality of radar cross sections includes radar cross sections common to the second subset of the plurality of radar cross sections and also includes radar cross sections different from the second subset of the plurality of radar cross sections. 18. The method of claim 17,
Wherein the first subset of the plurality of radar cross sections does not share radar cross sections with the second subset of the plurality of radar cross sections. 18. The method of claim 17,
Wherein adjusting the radar cross-section of the device comprises selecting different impedance values of the antenna of the device. 18. The method of claim 17,
Wherein the second data is derived from the first data or is a smaller subset of the first data. 18. The method of claim 17,
Wherein the second data is backwards compatible with the EPC Gen2 RFID protocol.
The method according to claim 1,
Wherein the encoding module uses the plurality of impedance values to encode the first data at the higher frequency and simultaneously encodes the second data at the lower frequency on the antenna. The method according to claim 1,
Wherein each symbol in a constellation of symbols used for communication through the backscattering is associated with a first associated impedance value in the first subset communicating a respective symbol and a second associated impedance value in a second subset Having an impedance value. The method according to claim 1,
And the second data is encoded based on the proximity of the impedance value selected for one of the two central radar values during the time length.

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